1. Field of the Invention
The present invention relates to a sheet processing apparatus for selectively performing a process such as an alignment, a binding or the like with respect to sheets fed thereinto from an image forming apparatus such as a laser beam printer or the like to deliver and stack the sheets.
2. Description of the Prior Art
Conventionally, a sheet processing apparatus, mounted in an image forming apparatus such as a laser beam printer or the like, includes an intermediate stacking portion for aligning a sheet fed thereinto from the image forming apparatus, a reference wall disposed in the intermediate stacking portion for making a positioning of a widthwise direction perpendicular to a conveying direction of the sheet, a stapler, secured to a position in parallel with the reference wall, for performing binding operations with respect to an aligned sheet bundle, a delivery roller for delivering the sheet or the sheet bundle from the intermediate stacking portion, and a sheet stacking portion for stacking the sheet or the sheet bundle thus delivered, where the sheet bundle thus stapled is sequentially stacked on a stacking tray of the stacking portion by the delivery roller.
In the foregoing conventional example, the sheet bundle in a staple mode is to be delivered onto the stacking tray by the delivery roller, but such a poor stacking might occur, for example, as that a front end portion of the sheet bundle is hanging down while being delivered, and therefore the front end portion of the sheet bundle thus hanging down is caught by a staple portion of a sheet bundle already stacked on the stacking tray, thus to push out the sheet bundle.
In addition, in the foregoing conventional sheet processing apparatus, since the stapler is structured to be secured on the side of the reference wall for positioning the sheet, in the case of a plural binding operation, the sheet where a first position has been bound is designed to conveyed as a bundle to a next binding location. At this moment, the sheet bundle is to be sent by the delivery roller to the sheet stacking portion on an upstream side in a conveying direction of the sheet bundle, and in the case that the sheet bundle, the front end side of which, for example, is curved downwardly during this sending process by its own weight, is then subjected to the next binding operation, a length between staples varies between a topmost sheet and a bottommost sheet of the sheet bundle due to a difference between an outer R and an inner R, with the result that upward floating of the sheets between the staples might occur.
Furthermore, in the foregoing sheet processing apparatus, in the case of a front end-one position binding operation, as a stacking amount is increased, thus to pile up the staple portions of the sheet bundles, a portion around the staple portion at the front end of the stacked sheet bundle becomes higher. Consequently, in order to improve a stacking property of the sheet bundle as well as to increase the number of stacking sheet bundles, it is required to guide, on the upper side, the front end of the sheet bundle to be delivered, so as not to be caught by the higher portion.
It is an object of the present invention to prevent a poor stacking where a front end portion of a sheet bundle to be delivered onto a stacking tray is caught by a staple portion of a sheet bundle already stacked on the stacking tray, thus to push out the sheet bundle.
It is another object of the present invention to prevent an upward floating of sheets generated between staples of a sheet bundle which has completed a process of binding at a plurality of positions, to improve a stacking property of a sheet bundle which has completed a front-end one-position binding operation, and the like.
A representative structure of the present invention for accomplishing the foregoing objects is a sheet processing apparatus including an intermediate stacking portion for aligning a sheet fed from an image forming apparatus; a reference wall placed on one side of the sheet in a widthwise direction perpendicular to a sheet conveying direction; a stapler for performing a binding operation with respect to one side of the sheets in the widthwise direction of the sheet bundle thus aligned by the reference wall; a delivery means for delivering the sheet or the sheet bundle from the intermediate stacking portion; a sheet stacking portion for stacking the sheet or the sheet bundle delivered by the delivery means; and a guide means provided above the sheet stacking portion and at an end portion on the stapler side of the sheet end portions in the widthwise direction of the sheet, the guide means supporting the end portion on the stapler side of the sheet bundle when the sheet bundle is delivered from the delivery means in a stapler mode where the binding operation is performed with respect to the sheet bundle.
According to the above structure, when the sheet bundle is delivered from the delivery means in the staple mode, the front end of the end portion on the stapler side of the sheet bundle is supported by the guide member, so the front end of the sheet bundle is not hanging down. Accordingly, this can prevent the sheet bundle thus delivered from being caught by a staple of a sheet bundle already stacked on the stacking tray to push out the sheet bundle stacked on the stacking tray. In addition, when a plural binding operation is performed with a stapling operation, since the sheet bundle is supported by the guide means on the stapler side, an upward floating of the sheets between the staples caused by the bending of sheet bundle between the staples can be prevented.
It is to be noted that, when the delivery means makes a delivered position of the sheet or the sheet bundle different, in terms of the widthwise direction of the sheet, between in the staple mode in which the binding operation is performed with respect to the sheet bundle and in the non-staple mode in which no binding operation is carried out, the guide means is not required to support the sheet in the non-staple mode.
Further, provided that the guide means has a structure including a straight portion set to have an angle the same as a delivery angle of the sheet bundle by the delivery means, when the binding operation at the numeral positions is performed in the staple mode, an upward floating between the staples can be prevented more certainly.
In addition, provided that the guide means has a structure having an R-shaped portion which is connected from the straight portion and is curving upwardly, the front end of the sheet bundle and the staple of the sheet bundle stacked on the sheet stacking portion can be prevented, more certainly, from interfering with each other. Furthermore, provided that the R-shaped portion has a slope inclining downwardly toward the other side of the sheet the sheet bundle can drop down more smoothly onto the sheet stacking portion.
Moreover, provided that the sheet stacking portion has a structure having a front-end fully-loaded detection means for detecting a fully-loaded state of the front ends of the sheet bundles and a rear-end fully-loaded detection means for detecting a fully-loaded state at the rear end of the sheet bundle, the fully-loaded state of the sheet bundles can be accurately traced if the sheet bundles are stacked and increased in bulk due to the staples.
Also, provided that the rear-end fully-loaded detection means has a structure detecting stacking heights in the staple mode in which the binding operation is performed with respect to the sheet bundle and in the non-staple mode in which no binding operation is performed with respect to the sheet bundle, independent maximum stacking conditions of the stapling state and non-stapling state can be changed respectively. More specifically, the rear-end fully-loaded detection means is realized as a contact sensor having a lower first detecting position in contact with the sheet bundle in the staple mode and a higher second detecting portion in contact with the sheet in non-staple mode.
Further, provided that a pushing means is provided in a portion on a top surface side of the guide means or the guide means is designed to move forward and backward on its own, leaning of the sheet bundles on the guide means can be eliminated, thus to be able to increase the number of stacking bundles on the sheet stacking portion.
It is to be noted that the sheet processing apparatus together with an image forming means for forming images on sheets as well as a conveying means for conveying the sheet where the image is formed may constitute an image forming apparatus.